Stabilizing apparatus



Sept. 13, 1949. 7 L. B. LYNN 2,481,853

STABILIZING APPARATUS Original Filed Nov. 23, 1940 2 Sheets-Sheet lINVENTOR v jazurazc-efil zm ATTORNEY STABILI Z ING APPARATUS 2Sheets-Sheet 2 Original Filed Nov. 23, 1940 WITNESSES: L INVEEgCE .34 MMW 9 mare/ ce 71 1].

BY 4) W, 7}), $04,

ATTORNEY Patented Sept. 13, 1949 STABILIZING APPARATUS Lawrence B. Lynn,Wilkinsburg, Pa., assignor to Westinghouse Electric Corporation, EastPittsburgh, Pa., a corporation of Pennsylvania Original applicationNovember 23, 1940, Serial No. 366,918, now Patent No. 2,381,161, datedAugust 7, 1945. Divided and this application September 11, 1944, SerialNo. 553,521

4 Claims.

This application is a division of my application, Serial No. 366,918,filed November 23, 1940, maturing into Patent No. 2,381,161, grantedAugust 7, 1945, relating to stabilizing apparatus constituting animprovement upon that disclosed and claimed in the patent of Hanna,2,381,160, granted August 7, 1945.

In said patent of Hanna, a pair of valves connected by a balancing leverare moved to vary hydraulic pressures bymeans of a pair ofelectromagnets to which currents are supplied by resistors. Thehydraulic arrangement, while having inherent positive stiffness(increasing displacement accompanied by an increasing opposing force),becomes unstable if the negative stiiiness (increasing displacementaccompanied by decreasing opposing force) due to the electromagnetsovercomes the positive stiffness. Hanna proposed to vary the currents inthe circuits differentially by having a fixed resistor in one circuitand a variable resistor in the other, the variable resistor havingcontacts tapped therealong. If the resistor resistances in circuit areequal with half of the variable resistor shunted, it will be apparentthat the currents in the circuits may be varied differentially byengaging and disengaging contacts so that the variable resistor may beadjusted to provide resistance in one circuit which is more or less thanthe fixed resistance in the other circuit; however, this arrangement hasthe disadvantage of a high negative stiffness because of the relativelylarge total currents required for operation, and, in consequence ofthis, the hydraulic apparatus has to be designed to give sufficientpositive stiffness for stability.

In accordance with my invention, the two circuits supplying theelectromagnets are each provided with a resistor, each resistor hascontacts tapped therealong, and the two groups of contacts are arrangedparallel with an actuator interposed therebetween. If the actuator ismoved away from mid position in one direction, the contacts of one groupare progressively engaged; if it is moved away from mid position in theother direction, the contacts of the other group are progressivelyengaged; and if it is moved toward mid position, then engaged contactsare thereby progressively disengaged. Preferably, with the actuator inmid position, a plurality of contacts of each group are engaged,whereby, with movement of the actuator away from mid position, theengaged contacts of one group will be progressively disengaged andadditional contacts of the other group will be progressively engaged,although the contacts and actuator may be so arranged that, with thelatter in mid position, all of the contacts are disengaged. Either typeof push-pull arrangement has the advantage of a smaller average fluxdensity in operating the electromagnetically-operated valves, with theresult that the negative stiffness is reduced, for'it will be apparentthat the total currents required will be relatively less thannecessitated in the Hanna arrangement. Therefore, with the reducednegative stiflness, the hydraulic apparatus may be designed forrelatively less total stiffness with the result that component parts maybe made smaller.

The currents supplied to the magnet windings should be such as to obtainmaximum sensitivity from the stabilizer without causing the gun to huntor vibrate. Insuflicient current causes a loss of sensitivity. On theother hand, too much current supplied to the windings increases thesensitivity to the extent that the gun will vibrate rapidly. Therefore,to assure of current supply in relation to positive stiffness of thehydraulic arrangement such that maximum sensitivity may be securedwithout hunting or vibration, I prefer to incorporate a stiffnessrheostat or potentiometer between the source of current supply and eachof the circuits supplying the magnet windings. With the push-pullarrangement of contacts and actuator, the total currents required foroperation of the electromagnets may be minimized; and, by adjusting therheostat or potentiometer means supplying the circuits, the currents forthe electromagnets may be adjusted to give a negative stiffness havingsuch relation to the inherent positive stiffness that the stabilizer mayhave maximum sensitivity without hunting or vibration.

An object of the invention is to provide, in connection with apparatusof the above character, an arrangement of resistors, contacts, and anactuator for the contacts such that the currents supplied to theelectromagnets for operating the magnetic valves may be varieddifierentially in opposite directions in such a manner that the totalcurrents required may be minimized in order to reduce the negativestiffness occasioned by the employment of electromagnets.

A further object of the invention is to provide, in connection with theimproved arrangement of resistors, contacts and actuator, stiffnessrheostats or potentiometers for supplying currents to the magnetcircuits so that such a relation of ne ative stiffness to positivestiffness may be had that the stabilizer has a high degree ofsensitivity with preservation of stability of operation.

Other objects and advantages will become more apparent from a study ofthe following specification when considered in conjunction with theaccompanying in which:

Fig. -l is a perspective view of a gun and its mounting with stabilizingapparatus applied thereto;

Fig. 2 is a schematic view showing partly in ..ing bod porti s o he la eei r e tarily shown at 3. $ta bilizing apparatus cooperates with thegunor body member tostabilize the latter about the trunnion axis tominimize angular deviations of the gun about that axis from aimedpositipn and due to disturbances. Such apparatus provides for movementof the tank body about the trunn on axis and itis adjustabl in afollow-up manner provide o anges in elevation- The stabilizing apparatusincludes a hydraulic motor device, at it, con ectin th s or ody memberand the supporting structureor tank, the motor device includ ng a evl ndr V a a piston i the cyl nder and d vid n the latt into p ess rechambers 1.3 and 1.4.- A pa oi p ps and I6 sirireh by a motor M ha e teir o l t op ning into ressure spac s which in u the c ambe s 1 and 1,4.Mo e particu a the pumps have their outlets. l1 and! c ed y p ages 19 nt9 the. p essure cha e ,Bv pess a ages 2.1 and 2.27. commun cate withthe passages 19 and 2. and they! provided with outwardlyefac ps valveseats 23 and 24 w t hi h cooperate valves. Ahead 25 connected by a Vbalancing lever 1, iulo prued at 2.8, It Will be appa nt hat, if, e thevalve is moved in a sin directi n, he lid d pressure in thecorresponding re sure space will. increase: and. cer The liquid pressureineach pressure space exerts force 011. it valve tending to npen it;and, as the valves are connect d by {the balancing lever, not only doesthe fulcrum of the latter opposethe resultant o the opening orces act non he two valves, but he ppo itd aet ns moments o S forces tend to beequalized by the lever, Movement of the lever from an equilibriumposition is opposed by in a i g resistance because i the i r as ndifierential of fluid pressure forces acting on the valves. Therefore,so In; as the valve tend to be pos tione by fluid Pressures, thehydraulic arren ement has positive stifiness. in rease in displac mentor dev ation b ing accompanied by increasing opp si g force- From the stu tu e sofar described, t W be ppa nt hat the pteesure in. the ham andI4 acting ifier entially on opposite sides of th pi ton; 2: may becontrolledby adjustin the a s 25 aud t-by me heo e valve-in a cl sindirection the other valve inan Opening direco There-fi re. iieoptrollips forces of. proper masnitudesa e apnliedtoproperly timedrelation to thevalvesrhvdraulie pressure may e deveiop d such that.theforceiiifierential thereof acting on motorde iee, at; l l l s sin epe tion by the latter to the' gun of stabilizing force. In other words,disturbing torque acting on the gun about the trunnion axis isaccompanied by the prompt developing of an opposing stabilizing torqueefiective thereon about the same axis. Furthermore, as liquid' frolnacontracting cylinder space may at all -timesescape *through thecorresponding by-pass, it will be apparent that the tank or supportingstructure is capable Of moving .an ularly about the trunnion axisrelative to the gun, whereby the tank is free to follow the terrainwithoutztheheby acting through the stabilizer todisturb substantiallythe aimed position of the gun.

The controlling .iorces applied to the Valves are developed response toangular displacement or deviation of the gun about the trunnion axis andto the 'velooity of such displacement or de-.

viation. The provision for control in response to velocity assures of astrong opposing force effective as displacement begins; and theprovision of means responsive to gravity, and by means of which angulardisplacement may be sensed, proe vides for control so. that the gun orbody member tends to return to the aimed or wanted position. Thedisplacement-sensing and the velocity sensi-ng means work together "toefiectstabilization of the aimed position, the major partof thestabili-zing eifor-t being developed in response to the velocity-sensingmeans and the :latter cooperating with the datum or gravity responsivemeans to secure return with a minimum of hunting, the velocity-sensingmeans acting in an anticipatory manner to oppose departure from thewanted or aimed position and in an anti-hunting manner to oppose returnto that position, the displacement and velocity effects actin jointly onthe hereinafter-described control device to obtain relizer.

' plate connected-tomove with the gun as the Referring now to thedisplacement and velocity sensing components, there is shown asupporting latter moves angularly about the trunnion axis. Thesupporting plate carries a gravity-responsive element, for example, thependulous'member 3| having asuppor-ting =pivot'3'2. A pendulous gyro 33is operative so that its spin axis seeks the vertical and its cooperateswith the pendulous member 3| to stabilize the latter with respect to thevertical plane of the pivot axis of the pendu lous member. r

The velocity-sensing means. comprises a second gyro 34 carried by'thesupporting plate 3d so as to process when the latter moves angularlywith the gun about the trunnion axis. The gyro 34 is a neutral one anditincludes a casing or frame 35 having a spinning body 3'36v journaledtherein and the casing is pivotally connected, at 3'1, 31, to upper andlower arms 38; '38' of yoke 39 attached to the plate 30. The gyro isarranged with its axis of spin :c-x extending transversely of themounting axis ofthe supporting plate .30 and its precession axis g-y,defined by the, axis of the pivots 31, 31, extending normally both tothe spin axis and to the mounting axis. Therefore, if the gun moves, thegyro will have precessional movement which is proportional to velocityof angular movement ofithe gun; A damper, at 34a, connecting thesupporting plate and the gyro so as to be effective about the precessionaxis of the latter, serves to filterout 4 3| and the velocity gyro 34comprises an actuating part 4| movable with the gyro 34 when the lattermoves about the precession axis y-y and an actuated part 42 carried bythe pendulous member. As the supporting plate carries thegravity-responsive means or pendulous member 3|, the velocity gyro 34,and the actuating and actuated components of the control device, at 40,it constitutes the means by which displacement and velocity may beutilized in effecting relative movements of the components of thecontrol device such that the desired resultant controlling effects maybe delivered from the latter.

As shown, the actuated part 42 comprises selfopem'ng leaf springcontacts 43 arranged as parallel groups 44 and 45 and the actuating part4| includes an insulating actuator 46 arranged between the groups ofcontacts and which operates, as it moves from mid position in onedirection, to progressively engage the contacts of one group; as itmoves from mid position in the other direction, to progressively engagethe contacts of the other group; and as it moves toward mid position, itprogressively disengages engaged contacts. Preferably, for reasonshereinafter given, the arrangement is such that, with the actuator inmid position, a plurality of contacts of each group are engaged.

While the contacts may be used to vary any suitable impedance devices,they are shown as bein tapped along resistors, the group of contacts 44being tapped along the resistor 41 and those of the group 45 beingtapped along the resistor 48, and the resistors 41 and 48 are arrangedin circuits 49 and 50 including windings 5| and 52 of a pair ofelectromagnets used for applying forces to the poppet valve aggregate.As the contacts of the group 44 are progressively engaged, successiveportions of the resistor 41 ar shunted to increase the current in thecircuit 49 and to increase the flux of winding 5|; and, as the contactsof the group 45 are progressively engaged, the current in the circuit 50is increased to increase the flux of the winding 52.

With the two poppet valves 25 and 2B interconnected by the balancinglever mechanism, both valves are normallyopen because of normal equalenergization of the windings 5| and 52, the magnetic forces exerted bythe windings on the balancing lever mechanism being balanced andconsequently such valves occupying a balanced mid position.

Assuming that the right-hand resistor 41 has been partially shunted bythe contacts of the group 44 due to relative movement of the actuatingelement 46 and the actuated element 42 as the result of rocking movementof the supporting plate 30, it will be seen that more current will flowthrough the coil 5| due to the decrease of resistance in seriestherewith, than through the coil 52; and, as a result, the balancinglever 21 will move in a counterclockwise direction which will result inmovement of the lower valve 26 in a closing direction and furtheropening of the upper valve 25. As a consequence of this, the pump l6will build up pressure in the pressure space, including the passage 20and the cylinder chamber M, and thereby bring about an increase inpressure in the lower part of the cylinder which will exert upward forceon the piston l2 therein so as to push upward on joint 55, which issecured to the gun 5, to apply a clockwise stabilizing torque to the gunabout the axis of its trunnions 6.

If, on the other hand, the displacement were in the opposite directionso that the left-hand resistor 48 were shunted, coil 52 would beenergized to a greater extent than coil 5|, causing movement of theupper valve 25 in a closing direction and building up or pressure in thepres sure space including the conduit l9 and the cylinder pressurechamber l3, the increased pressure above the piston l2 resulting incounterclockwise stabilizing torque applied to the gun 5 about itstrunnion axis.

The hydraulic pressures in the stabilizer cylinder H are controlled bytheir respective valve currents. As the currents and magnetic fluxdensities are increased, negative stiffness is also increased. Regardingthe definition of stillness, a body is said to have positive stillnessif displacement is opposed by increasing resistance, as with a springwhere increase in displacement is accompanied by increase in force. Anelectromagnet has negative stillness, since, as the armature isattracted towards the core, the magnetic pull increases. If the poppetvalves of the valve aggregate be considered to the exclusion of themagnets, it will be apparent that the liquid pressure forces acting onthe valves cause the aggregate to seek a position placing such forces inequilibrium and that displacement from equilibrium position isaccompanied by increasing opposing force (positive stiffness).Disregarding the valves and considering only the magnets, instead of thedisplacement being accompanied by increasing opposing force, the forcetends to increase the displacement (negative stiffness). Since themagnets act in opposition, it will be obvious that, for the samedifierential force, a greater total current and, therefore, greatertotal flux, will be required where a fixed current flows through onemagnet and the current through the other is caused to vary above andbelow the first (Hanna, aforesaid,) than is required in the presentarrangement where both currents are varied. The present arrangement iscapable of exerting the same force as that of Hanna, aforesaid,rwithless aggregate current and therefore less magnetic flux; and, since thenegative stiilness is a function of flux, it being remembered that theforce exerted by a magnet on an armature varies directly as the flux andinversely as the square of the distance, it will be apparent that thenegative stiffness is reduced. If such negative stiffness becomesgreater than the positive stiffness arising from the hydraulic pressuresacting on the valves, unstable operation occurs. The range ofinstability may be varied by changing the valve clearances, air gaps orother constants, and may be kept low by keeping the total valve currentsat a minimum.

Valve operation with a fixed current in one coil and a variable currentin the other, as described in the aforesaid Hanna. patent, requiresrather substantial flux densities so that the range of unstableoperation is appreciable.

By'reducing the current in one valve operating electromagnetic coil asthe current in the other coilis increased (class A push-pull), theaverage flux is reduced and stability isimproved.

Another'method of operation comprising the provision of two sets ofcontacts, one on the right hand and the other on the left hand of theactuating member and with all of the contacts normally in open positionwith the actuator in mid position. This type of operation (class Bpush-pull) further reduces the average flux density and greatly improvesstability.

Push-pull operation, such'as involved in" either operation.

fclass A, or class 3 described 'above, the gun stabilizer has beenobtained by employing two groups of contacts as shown inf-1g. 2 andrelated .to the actuator so that, with the "latter in mid position, aplurality of contacts of each group are engaged. I

Acha-nge in angular position of the gun '5-about the axis of thetrunnions 6 causes --more leaves of-one group of contacts to be closedor tower of the other to be closed, or both. +By choice of Width of theactuating member 45, it is possible toobtain any-oi the seevral classesof push-pull Class A appears "to be preferable, since the ci'zntacts areimmediately responsive to the slightest movement of the actuator fromits acid :position.

It is desirable to-have-equal increments of corrective torque for equalincrements of angular displacement of the gun, As applied to the gunstabilizer, ior example, fifteen leaves of the contacts may close forone degree angular displace- Jnent of the gun, or one leaf for each tourminutes. The pressures as controlled by the valves are approximatelyproportional to the square of the valve currents, being distorted bypump characteristics and other factors. Actual graphs of correctivetorque against valve current were obtained by measurement on a fullscale model and stabilizer. From these, the currents to produce uniformsteps of torque were determined, and resistance steps (of unequalvalues) to give these currents calculated. Resistors '41 and 48 weremade in steps of these values and connected to the'ir respective groupsof contact leaves.

Thus a linear relation betweh angular vgun means is provided for varyingthe currentssupplied to the circuits having the resistors and thedisplacement and restoring torque is obtained. The rate of change oftorque to dispiac'ement, or the sti ifness of the stabilizer, isdetermined by the voltage applied to the circuit and may be varied byresistance means, such as rheos'tats orpotentiometer's 51 and 58'. Suchrheostat o'r potentiometer means may provide for independent ad.justment of each coil actuating circuit and assures of currents beingsupplied to the circuits such that the negative stiifness exerted on thevalve aggregate will be in such relation to the positive stiffnessthereof that the apparatus may be adjusted so as to be adequatelysensitive and so as to avoid hunting.

During recoil fol-lowing firing of the gun, e xcessively largeunbalancing torques exist because of the displacement of the center ofgravity to a position to the rear of the trunnion aids for periods ofabout one-half second. Because of these unbalancing eiiects occurringonly after each shot and persisting for relatively short periods,and'because of space and weight limitations imposed, it is undesirableto build the stabilizer large enough to accommodate these largedisturbances, which are many times the magniture of the disturbancestransmitted to the 'g'u due to motion of the tank or vehicle.

I avoid the necessity of building such a large stabilizer as would benecessary in the system shown and claimed in the aforesaid Hanna patentby supplying a highcurrentto a valve coil during recoil to couple thegun closely to its mount during this period of unbalance-. As moreparticularly disclosed and claimed in my patent aforesaid of which thepresent application is a division, the high value current may besupplied by an additional voltage applied tothe coilcirsuit by theauxiliary coil 60 through a-switch 6| operated by the motion of the gunundergoing recoil. In this manner, additional energization the backwardflow of liquid through uiepump when the pressurefcreated by the downwardmovement of the piston becomes in exeesstr the peak delivery pressure ofthe unis. 'Thzfdre, having cared for recoil" I particular manner, thestabilizer and its cc'int'rol mayte'aesigned to meet stabilizingrequirementsnecessitated because of motion or iheveni'cle of i From theforegoing; it will be apparent that I have provided, for any suitable"regent paratus having a controlling m mber-much operates with inherentpositive stiffness/a pair of electromagnets for moving the controllingmember in opposite directions, together with means for controlling theelectriccu'rr'eiits required to energize the magnets so that such rentsmay be kept sufficiently small to avoid'the negative stiffnessintroduced because of the magnets from overcoming the inherent positivestiffness and therebybring about unstable operation of the apparatus. Onthe other hand; sensitivity 7 of the apparatus is increased byincreasing the currents and, therefore, negative stiffness. Therefore,the problem arises of providing the sensitivity desired withoutinstability;; and it is for this reason, that rheostat or potentiometerflexible contacts. Such rheostat or Lpotentiom .etcr means makes itpossible to overcome individual variations in positive stiffness ofrcgulators, the desired sensitivity and stability in each case beingsecured by rheostat or potentiometer adjustment. 7

While the invention has been shown in but one form, it will be obviousto those skilled in the art that it is not so limited, :but issusceptible of various changes and modifications without departing fromthe spirit thereof.

What is claimed is:

1. In apparatus 'for controlling a hydraulic motor so that the latterdrives a 'pivo'tally-moun'ted body about its mounting .aXis in suchmanner as to stabilize the body by, minimizing oscillatory disturbancesof the latter with respect to such axis, said apparatus including-a pairof passages respectively supplied with liquid from a pair "ofpressure-developing devices and supplying liquid to said motor; each ofsaid passages having} an escape port whose discharge end is formed as avalve seat; valves movable toward and away from the seats to vary thepressures in the passages; a balancing rocker fulcrumed' at anintermediate point and having its ends connected to the valves so thatopening liquid pressure forces act continuously on the latter and on therocker with the moments of such forces about the fulcrum axis in opposedrelation, whereby there is provided a positive stifiness efiect adequatefor stability of the apparatus; apair of electro-m'ag-nets for applyingcontrolling forces to' th'erocker with the moments of such forces aboutthe fulcrumaxis in opposed relation and with, the differential of themoments ofliquid pressure forces normally balancing the difierentialioithe moments of controlling forces; and means for energizing said magnetsso that change inthedifferential oi moments of the controlling forcescauses the rocker and the valves to move to change the differential ofmoments of the liquid pressure forces until the balanced relation ofmoments is reestablished and so that the negative stiffness effect ofthe magnets is maintained sufliciently less than said positive stiffnesseffect for operation of the apparatus with adequate sensitivity; saidlast-named means comprising a pair of circuits with the windings of theelectro-magnets included in the respective circuits, a resistor in eachcircuit, self-opening leaf spring contacts tapped along each resistorand arranged to be progressively engaged to shunt successive portions ofthe resistor and to be progressively disengaged to include such portionsin circuit, said contacts being arranged as a pair of parallel groups,and an actuator interposed between the groups of contacts and movableaway from mid position, in one direction, to progressively en age thecontacts of one group and, in the other direction, to progressivelyengage the contacts of the other group and movable toward mid positionto provide for disengagement of engaged contacts.

2. Apparatus as claimed in claim 1 wherein a plurality of contacts ofeach group are held closed by the actuator when the latter is in midposition.

10 3. Apparatus is claimed in claim 1 with variable resistance means forvarying the current supplied from a suitable source to each of thecircuits. 4. Apparatus as claimed in claim 1 with a pair of variableresistances arranged in the respective circuits between a suitablecurrent source and said resistors.

LAWRENCE B. LYNN.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,921,172 Taylor Aug. 8, 19332,188,834 Fischel Jan. 30, 1940 2,199,910 Cunningham May 7, 19402,234,326 Tiebel Mar. 11, 1941 2,246,306 Kovalsky June 17, 19412,351,977 Kronenberger June 20, 1944 FOREIGN PATENTS Number Country Date445,351 Great Britain 1936 Certificate of Correction l Patent No.2,481,853 September 13, 1949 LAWRENCE B. LYNN It is hereby certifiedthat errors appear in the printed specification of the above numberedpatent requiring correction as follows:

Column 3, line 49, for the Words it valve read its valve; line 58, forvalve read valves; line 70, for to before properly read in; column 4,line 47, for and its read and it; line 62, for and its read and withits; column 5, line 41, for ar before "shunted read are; column 6, line67, for comprising read comprises; co umn 7, line 12, for seev'ral readseveral; lines 60 and 61, for magniture read magnitude; column 10, line1, for is before claimed read as; and that the said Letters Patentshould be read with these corrections therein that the same may conformto the record of the case in the Patent Office.

Signed and sealed this 31st day of January, A. D. 1950.

THOMAS F. MURPHY,

Assistant Commissioner of Patents.

